Delay Alignment Modulation for Single-Carrier Broadband Transmission
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Solution Overview
Problem
Existing broadband communication technologies like OFDM face issues such as high peak-to-average-power ratio (PAPR), severe out-of-band emission, and vulnerability to Doppler frequency offset, which increase complexity and cost, while conventional single-carrier methods require complex equalization and increase implementation complexity.
Innovation Solution
A channel equalization-free single-carrier delay alignment modulation method that uses multi-path sparsity and large antenna arrays to perform delay compensation and path-based beamforming, eliminating inter-symbol interference (ISI) and reducing signal processing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM is used for broadband communication, then high-rate communication is achieved, but high PAPR causes nonlinear distortion of power amplifiers
Solution Approach 1:
The patent extracts and eliminates the multi-carrier structure that causes high PAPR, retaining only the single-carrier structure. By removing the harmful multi-carrier superposition while keeping the beneficial high-rate communication capability through single-carrier frequency domain equalization, the invention resolves the contradiction between communication rate and nonlinear distortion.
Solution Approach 2:
The patent changes the key parameter from multi-carrier frequency domain to single-carrier frequency domain, transforming the signal structure. This parameter change maintains the ability to achieve high communication rates while fundamentally altering the PAPR characteristic to avoid nonlinear distortion of power amplifiers.
2Productivity
If OFDM is used for broadband communication, then high-rate communication is achieved, but severe OOB emission causes interference to adjacent channels
Solution Approach 1:
The patent removes the multi-carrier structure responsible for severe OOB emission with large sidelobes, keeping only the single-carrier structure. This extraction eliminates the harmful frequency domain characteristics while preserving the high-rate communication capability through alternative single-carrier modulation techniques.
3Reliability
If conventional single-carrier equalization is used, then ISI is mitigated, but equalization complexity and cost significantly increase
Solution Approach 1:
The patent replaces the complex time-domain equalization mechanism (FIR filter with multiple taps) with a simpler frequency domain processing approach. By substituting the mechanical filtering operation with frequency domain multiplication, the invention achieves the same ISI mitigation effect with significantly reduced complexity.
4Reliability
If more taps are added to FIR filter for severe delay spread, then ISI mitigation is improved, but equalization complexity and cost significantly increase
Solution Approach 1:
The patent extracts and removes the complex time-domain equalization structure entirely, replacing it with frequency domain processing. This extraction eliminates the need for multiple FIR filter taps while maintaining effective ISI mitigation for channels with severe delay spread through the single-carrier frequency domain equalization approach.
Data Source
AI summary
The present invention discloses a channel equalization-free single-carrier broadband transmission method, including the following steps: obtaining a number of temporal-resolvable multi-paths, and delays and channel gain vectors corresponding to the multi-paths based on a channel impulse response; deliberately introducing, by a transmitter, a corresponding delay for a symbol sequence, so as to perform delay compensation, so that all multi-path signal components arrive at a receiver simultaneously and constructively after propagating over a time-dispersive channel, thereby avoiding inter-symbol interference in broadband transmission; and utilizing, by the transmitter, multiple antennas to perform path-based beamforming design. A time-dispersive channel can be transformed into a frequency-flat channel by means of the path-based ZF beamforming and delay alignment modulation. The present invention further proposes a channel equalization-free single-carrier broadband transmission system. In the present invention, with delay alignment modulation and the path-based beamforming, the issue of inter-symbol interference in broadband communications is resolved, without requiring the channel equalization or multi-carrier transmission, thereby achieving the low-complexity single-carrier broadband communication.